Phytochemical investigation of the 95% EtOH extract of the dry fronds of Conyza japonica (Thunb.) Less. resulted in the isolation of three new labdane diterpene glycosides, (3β,13S)‐13‐O‐α‐L‐rhamnopyranosyllabda‐8(17),14‐dien‐3‐yl α‐L‐rhamnopyranoside (1), (3β,13S)‐13‐O‐α‐L‐rhamnopyranosyllabda‐8(17),14‐diene‐3‐yl 2‐O‐acetyl‐α‐L‐rhamnopyranoside (2), and (3β,13S)‐13‐O‐α‐L‐rhamnopyranosylabda‐8(17),14‐dien‐3‐yl 6‐O‐acetyl‐β‐D‐glucopyranosyl‐(1→2)‐α‐L‐rhamnopyranoside (3), together with their aglycone, (13S)‐labda‐8(17),14‐diene‐3,13‐diol (4). Their structures were characterized by spectroscopic analyses and chemical correlations, including 1D‐ and 2D‐NMR, and HR‐ESI‐MS. Furthermore, compounds 1–3 appeared to be promising as active agents against the tested pathogen fungi and oral pathogens as they possessed moderate cytotoxic properties.